Method for cutting a gear, gear-cutting tool and gear-cutting machine

Abstract

A method for cutting a gear (4) from a metal workpiece (2), in which a tooth flank, still having an oversize compared with its predefined final geometry, of the gear is hard finished, to create a mirroring property, existing in the final geometry, of its surface, in one or more cutting passes in cutting engagement with one or more cutting tools (10), fed thereto, with a geometrically undefined cutting edge made of cutting grains incorporated in a binder matrix, wherein, in one cutting pass of a cutting tool (10b), not only is this surface property worked towards by an elastically resilient mounting, set via the binder matrix thereof, of the cutting grains but also a cutting reduction in the oversize of at least 2 μm is brought about at the tooth flank by compressive prestressing which is set via the feeding of the cutting tool and to which the cutting engagement is subjected; and a gear-cutting tool and a machine tool therefor.

Description

[0001] The invention relates to a method for machining the gearing of a metallic workpiece, in particular in continuous gear grinding, in which a tooth flank of the gearing, which still has an excess compared to its predetermined final geometry, is hard-finished in one or more machining passes in machining engagement with one or more machining tools supplied for this purpose, with cutting grains of geometrically undefined cutting edge embedded in a bonding matrix, in order to produce a mirror-like property of its surface existing in the final geometry, a use of a gearing tool designed for such a method and a gearing machine designed for this purpose.

[0002] When gears with a predetermined final geometry (target dimension) are to be produced, a stock allowance is left over during, for example, machining processes using soft machining. This stock allowance is then removed after hardening the gear by means of hard / finishing machining. Hard / finishing machining can again be performed by machining with a geometrically defined cutting edge (e.g., by hard skiving), or with a geometrically undefined cutting edge through grinding processes such as profile grinding, gear grinding, or scraping (gear honing).

[0003] For typical applications, such as gear wheels in the automotive industry, the remaining stock removal can be on the order of 0.1 mm, or approximately 100 µm. Using conventional techniques, this stock removal is achieved in several machining passes, each with a deeper feed rate. This involves one or more roughing passes, in which the majority of the stock removal is achieved, followed by one or more finishing passes, in which the remaining stock removal after roughing is reduced to the final geometry. For example, in the above case of a 100 µm stock removal, 90 µm can be removed in one roughing pass, and the remaining 10 µm are removed in one finishing pass.

[0004] For both roughing and finishing, a ceramic bond is typically used to achieve the desired stiffness of the machining tool, for example a grinding screw for gear grinding; with regard to the abrasive, abrasive grains made of corundum or sintered corundum are often used, not least for cost reasons.

[0005] Furthermore, grinding allows for the introduction of tooth flank modifications such as crowning or settling. Both dressable and non-dressable grinding tools can be used. All of this is familiar to experts and described, for example, in Thomas Bausch's *Innovative Gear Manufacturing*, 3rd edition, Expert-Verlag.

[0006] The combination of roughing and finishing passes described above can produce gear surface finishes with a roughness depth Rz of up to approximately 2.5 µm (with arithmetic mean roughness values ​​Ra in the range of approximately 0.3 to 0.6 µm). The surface after such machining and with these roughness values ​​appears matte. However, users are increasingly demanding higher surface qualities in terms of lower surface roughness, to the point where the surface appears mirror-like.

[0007] To achieve these additional requirements, the gear teeth, already prepared by roughing and finishing, undergo a polishing process that essentially only polishes the gear surface to lower roughness values. Such a process was presented, for example, by Reishauer at the WZL Precision Machining Seminar 2015 as polishing grinding using an elastic bond in a grinding worm section. This process is carried out immediately after the conventional grinding operation without interrupting the machining process and has only the task of reducing the peak height of the roughness profile without altering the flank topography of the gear teeth in the active area. A roughness profile according to DIN 4768 with Rz of 0.73 µm and Ra of 0.08 µm is specified as achievable with this polishing grinding process.

[0008] As a further process principle within the same framework, a so-called fine grinding stage has been proposed. For this stage, grinding worms with ceramic bonds are typically used with a finer grinding wheel grit to reduce both the peak height and the groove depth of the roughness profile without altering the flank topography of the gear teeth in the active area. This fine grinding can be performed in the finishing stage or in an additional machining stage immediately following the conventional grinding process without interrupting the machining process. However, it only achieves a roughness profile of Rz of 1.35 µm and Ra of 0.21 µm, and thus does not yet meet the roughness parameters of a user-defined target of Rz less than 1 µm and Ra less than 0.1 µm.The polishing and grinding process proposed by Reishauer achieves a significant improvement in the functional properties of the gear teeth with comparatively little effort. The mirror-like surface of the gear teeth after polishing is also clearly visible on the presented example workpieces. It is stated that the change in surface texture occurs additively over time for both polishing and fine grinding.

[0009] EP 3 241 640 A1 discloses a gear grinding process including a fine grinding or polishing grinding pass with a worm-shaped grinding tool having two different areas but the same profile, wherein these two areas are operated with different swivel angles.

[0010] The invention is based on the objective of further developing a method of the type mentioned at the outset with regard to a satisfactory compromise between gear surface quality and process control.

[0011] This problem is solved by the invention through a method with the features of claim 1. For this purpose, it is provided that (with a radial overfeed of at least 20 µm and at most 100 µm caused by a negative allowance above the final geometry, which is referenced as a reference)

[0012] In a machining pass of a machining tool, this surface property is achieved both by an elastically compliant mounting of the cutting grains set via its bonding matrix and by a cutting allowance reduction of at least 2 µm on the tooth flank by a compressive preload set via the feed of the machining tool, to which the machining engagement is subjected.

[0013] The invention is based on the understanding that satisfactory surface properties, on the one hand, and advantages for the machining process itself, on the other, can be achieved by still reducing the cutting edge allowance on the tooth flank, despite the desired surface properties and the elastically compliant mounting of the cutting grains achieved via the bonding matrix. This is accomplished by applying a compressive preload via the feed of the machining tool. For various applications, this allows this machining pass to be performed immediately after (even after only) a roughing pass, thus eliminating the need for a finishing pass and consequently enabling shorter cycle times, as will be explained in more detail below.

[0014] For the purposes of this disclosure, a reflective surface property is present at an average roughness depth (RZ) of 1.35 µm or less. During the cutting removal of at least 2 µm according to the invention, the boundary between the core area and the profile groove area, as defined in ISO 13565, of the roughness profile of the tooth flank surface machined by the machining tool with elastically compliant bearing of the cutting grains is exceeded during material removal. Thus, not only are the peaks of the profile broken, but essentially the existing roughness profile prior to the cutting removal is eliminated and replaced by a newly generated roughness profile, which exhibits the reflective property after machining with this tool.In a further preferred embodiment, during the cutting removal process, material is removed over more than one-third of the profile groove area, and preferably over more than two-thirds of this area. It is also possible for the profile groove area to be almost completely or even completely removed.

[0015] In this context, in a particularly preferred process design, more than 3 µm, preferably more than 4 µm, and especially more than 5 µm of stock is removed in this machining pass, and / or less than 12 µm, preferably less than 10 µm, and especially less than 8 µm. This allows, firstly, a lower sensitivity to the preceding roughing operation. Secondly, by limiting the stock removal, harmful effects from excessive compressive stresses are avoided.

[0016] The compressive preload is achieved by setting the machine axis for, for example, a radial feed of the tool to the workpiece higher than a reference setting that would be used to achieve the desired material removal with a less compliant tool (setting for negative stock removal). For example, the grinding worm, which performs a preliminary stock removal before the machining pass of the cutting tool with its elastically compliant bearing of the cutting grains, can be used as the reference to which the following values ​​refer. Preferably, when converted to such a reference-related radial overfeed of a machine axis, an overfeed of at least 28 µm, in particular at least 36 µm, and / or at most 90 µm, in particular at most 80 µm, and in particular more preferably at most 70 µm, is set.The absolute numerical values ​​for radial feed can vary from machine tool to machine tool, as their elastic compliance must also be taken into account. These values ​​must be determined for the first time before initial use, for a given machine and workpiece configuration, for the machining tool with its elastically compliant cutting edge bearings, or retrieved from data sets containing these values ​​obtained through experimental tests or precise numerical simulations.

[0017] Regarding the cutting or abrasive grains, a Knoop hardness (in N / mm²) of more than 23,000, preferably more than 25,000, and particularly more than 27,000, is preferred. This ensures good cutting performance. Furthermore, if individual cutting grains break, "fresh" cutting edges are regenerated, resulting in satisfactory overall tool durability and, in particular, satisfactory cutting performance until the next required dressing.

[0018] Regarding the cutting or abrasive grains, silicon carbide (SiC), particularly green or black, is preferred as a component, especially as the predominant component. Grain mixtures with preferably at least 30%, more preferably at least 50%, and particularly at least 70% SiC are also considered, especially with corundum / sintered corundum as a further component of the mixture.

[0019] Preferred grain sizes for the abrasive grain used are in the range of greater than 5.5 µm, particularly greater than 7.5 µm, and more preferably greater than 8.5 µm. However, it is also preferred that the grain size be less than 18 µm, preferably less than 16 µm, and particularly less than 14 µm. According to the regulations of the FEPA (Federation of European Producers of Abrasives), for example, an abrasive grain size of 9.4 µm corresponds to a screen mesh size of 600 mesh, and an abrasive grain size of 6.5 µm corresponds to a mesh size of 800.

[0020] In terms of materials, it is preferably provided that the elastic setting includes a material selection for the bonding matrix as a plastic material or a rubber material, in particular polyurethane.

[0021] The elasticity of the machining tool with the elastically compliant mounting of the cutting grains thus operates within a range where, on the one hand, a walking effect is still possible, and on the other hand, the minimum removal of material required for cutting according to the invention still occurs. In this context, it is particularly preferred that the modulus of elasticity (Young's modulus) of the machining tool, measured in GPa, is less than 20.0, preferably less than 18.5, particularly less than 17.0, and / or greater than 10.0, preferably greater than 11.5, particularly greater than 13.0. The Young's modulus can be determined using a sonic measurement, as is already used for quality control of gear cutting tools, e.g., with measuring systems from GrindoSonic®.For this purpose, the tool, which is supported, for example, by a three- or four-point bearing, is set into vibration by an exciter, and the Young's modulus is determined using a sensor that detects the tool's frequency response to the excitation, assuming the tool's density is known (this technique is used in tool inspections to detect tool damage in the event of higher frequency suppression). The values ​​above refer to the tool used for this machining operation (and only to it).If a combination tool is used, designed in one area for machining and in an adjacent area for roughing, and equipped with a ceramic bond, measurements of the combination tool will yield correspondingly higher Young's modulus values ​​of the overall composite, approaching 30 GPa, corresponding to typical Young's modulus values ​​of ceramic-bonded grinding tools of approximately 34 GPa. Pure polishing tools, as explained earlier, have Young's moduli of only about 10 GPa, or even below 5 GPa, depending on their intended use.

[0022] It is therefore intended that softer tools will be used than the ceramic bonds usually used for roughing and finishing, but on the other hand, harder tools will be used than those intended purely for polishing tasks.

[0023] With regard to the surface roughness of the average roughness depth (Rz), a value of less than 1.2 µm, preferably less than 1.1 µm, more preferably less than 1.0 µm, and particularly less than 0.9 achievable and intended after this machining pass; for the arithmetic mean roughness value Ra, values ​​of less than 0.12 µm, particularly less than 0.10 µm, are also achievable. Values ​​of less than 0.08 µm have even been achieved (see below). It is further preferred that the sum of the core roughness depth Rk and the reduced peak height Rpk (determined via the Abbott curve) is less than 0.6 µm, even less than 0.5 µm, or even less than 0.4 µm. For the reduced groove depth Rvk, values ​​no larger than the order of magnitude of this sum are preferred; however, Rvk values ​​that are 50% of the core roughness depth Rk, approach or even exceed it, are certainly acceptable.

[0024] Preferably, the cutting speed (vc ) of this machining pass, measured in m / s, is greater than 42, preferably greater than 45, in particular greater than 48, and / or less than 80, preferably less than 72, in particular less than 66.

[0025] As mentioned above, a particularly preferred process design provides that the machining pass discussed so far is a subsequent machining pass preceded by machining, particularly roughing, which reduces the stock removal by a total of more than 30 µm, preferably more than 50 µm, and especially more than 70 µm. In this context, it is also preferably provided that the preceding machining comprises at most two machining passes, and in particular only one. In the latter of the preferred variants, two machining passes are therefore sufficient: a roughing pass, which in this case removes the total stock removal of preferably more than 50 µm or more down to the stock removal left for the machining pass of the elastic bearing and compression preload. This results in significant cycle time savings by completely omitting the usual finishing machining pass.

[0026] The variant with two (roughing) machining passes is preferably used when the total stock removal exceeds 80 µm, 90 µm, or even 100 µm, and / or significant asymmetries are present in the hardened pre-gearing. In this case, a material removal rate of at least approximately the same for both roughing passes is generally preferred; in any event, each machining pass should preferably remove more than 30 µm, and particularly more than 40 µm, of stock. Here, too, cycle time can be saved by omitting the finishing pass, which is typically performed at a slower speed.

[0027] Particularly in the case of low quality of the pre-machining of the gear teeth, such as a runout error and / or a pitch error of (each) more than 60% or even 65%, especially even 70% of the total allowance q, it may well be provided, in the case of carrying out two machining passes before the machining pass with the machining tool, to make the distribution of the material removal between the first and the second of these upstream passes more asymmetrical, with less material removal in the second of the preceding machining passes. In one possible embodiment, for example, for an average surface roughness depth RZ obtained (to be obtained) after treatment with the machining tool with elastically compliant mounting of the cutting grains, an asymmetry factor Δq / q (with Δq=|q 1 -q 2 | and q=|q 1 +q 2 |) and q 1 , q 2 removal in the first and second respectively could be used.The second pass is assumed to be equal to or less than g2, where . g 2 = 0 , 6 − 2 / 5 π arctan k R Z μm − R 0 , with k=80, R 0 =1.2, preferably R 0 =1.15, further preferably R 0 =1.1, and even more preferably R 0 =1.05, in particular R 0 =1.0. Alternatively or additionally, it is preferred that the ratio Δq / q ≥ g1, with g 1 = β 1 − H R z μm − R ′ 0 with R' 0 =1.0, preferably 1.05, in particular 1.1 and β=0.4, preferably 0.5, in particular 0.6, and the Heaviside function H(x).

[0028] For typical applications of gear-ground gears in the module range of less than 6 and gear widths up to 150 mm, correspondingly short machining times can be achieved in the preferred variant with only two machining passes in total. In the process design with two passes and the machining pass of the elastically compliant bearing, satisfactory machining times for achieving the desired surface properties in the final geometry are always achieved, which are still at least no higher than with conventional methods.

[0029] In this context, a ratio of feed rate of the subsequent machining pass to feed rate of the preceding pass of more than 1.4, preferably more than 2, particularly more than 2.5, and even more than 3, is preferred. A ratio of 4 or higher is even conceivable. For conditioning the grinding tool, the usual dressing systems consisting of form and profile rollers are available. Flexible, tool-specific, or multi-ribbed dressing tools should also be mentioned. Toothed or radius dressers can also be used. The conditioning process can be designed analogously to a conventional grinding process, consisting of a combination of roughing and finishing strokes.

[0030] Furthermore, the invention relates to the use of a gear cutting tool according to claim 12.

[0031] Furthermore, the invention protects a machine tool for machining the gearing of a metallic workpiece, which is equipped with a control device for carrying out the method according to the invention.

[0032] Further features, details and advantages of the invention will become apparent from the following description with reference to the accompanying figures, of which Fig. 1 schematically shows a gear grinding machine, Fig. 2 schematically shows an axial section through a snail-shaped tool, and Fig. 3a, b Abbott curves for two machined gear teeth are shown.

[0033] An embodiment of the invention is explained in more detail below for continuous gear grinding. A gear grinding machine suitable for this purpose has a workpiece spindle or table spindle 80 mounted in a machine bed 40 on the workpiece side, on which a gear 2 is mounted, which is already pre-cut and has teeth 4. The type of gear 2 and teeth 4 is not further restricted; a cylindrical gear is shown, but the invention is not limited to this and could also machine other types of teeth. In the case of shaft-shaped workpieces, a [missing information] can be used for this purpose. Fig. 1 A riding stock not shown will be provided.

[0034] On the tool side, a slide arrangement is provided that holds and positions the machining tool 10 in the form of a grinding worm. Specifically, as in Fig. 1 Three linear motion axes X, Y and Z are provided, which can adjust the relative position of the tool 10 to the work wheel 2 via CNC-controlled machine axis movements from a control 99.

[0035] A linear slide 50 is provided for a radial (X) feed movement. This carries a vertical slide 60 for a machine axis Z running parallel to the workpiece rotation axis C. A further support 70 is rotatably arranged relative to the vertical slide 60, pivoting along the X-axis direction (swivel axis A). The support 70 also includes a tangential slide (Y-axis) with which the tool 10 can be moved along the tool rotation axis. In the Fig. 1 In the depicted situation with swivel angle A=0, the tool rotation axis runs in the Y-direction of the Fig. 1 The depicted rectangular coordinate system X, Y, Z. The axis of rotation of the tool about its own axis is designated as the axis of rotation with B, the axis of rotation of the workpiece is designated as the axis of rotation with C.

[0036] As described, the design can therefore be a known structure for a gear grinding machine, and alternatively, other design configurations and machine axis distributions can also be provided.

[0037] At the in Fig. 2 The schematically depicted worm-shaped tool 10 is a combination tool with two coaxial sections 10a and 10b that are rotationally fixed to one another in this embodiment. Section 10a, in this embodiment, is a grinding worm designed for roughing gears in a continuous gear grinding process, particularly with a ceramic bond, as is well known in the prior art. The other section 10b, in this embodiment, is also a worm-shaped tool, which, particularly with regard to its worm parameters, can be and is identical to section 10a. The width of 10b corresponds to the minimum engagement width between tool 10 and gear 4, and a maximum of half the grinding wheel width (10a = 10b), often in the range of 60 mm.

[0038] In this embodiment, the Young's modulus of section 10b, when measured in isolation, is 13.6 GPa. Furthermore, in this embodiment, the bonding matrix is ​​made of a polyurethane material, and the abrasive grains are made of green silicon carbide. As explained in more detail below, section 10b of the screw 10 serves to machine a roughened tooth profile 4 to its final geometry with the desired surface properties by material removal, without an intermediate finishing pass (which is usually performed, for example, with section 10a of the screw 10).

[0039] For this purpose, the excess material relative to the final geometry is first removed in one or more roughing passes, leaving a residual stock allowance of, for example, 6 µm in this embodiment. This residual stock allowance is thus considerably smaller than is usually left for a subsequent finishing pass during roughing (typically, the finishing process removes approximately 20 µm of material). Subsequently, without performing a finishing pass, the screw section 10b is used to remove the remaining residual stock allowance to the final geometry in just one machining pass in this embodiment. By using a higher radial (X) feed than is required to achieve the final geometry with a non-flexible tool such as section 10a, the screw section 10b is brought into continuous gear grinding engagement with the toothing 4.Due to the combination of the flexibly designed screw section 10b with the preload set to negative allowance, material is removed only down to the final geometry, while maintaining a high surface quality. Furthermore, because the machining tool is still harder than that used for polishing alone, significantly more material is removed than with conventional polishing.

[0040] Two specific examples of implementation are described below.

[0041] In a first embodiment, a gear with a module of 3 mm, 22 teeth, and a pressure angle of 20°, which has helical teeth with a helix angle of 20°, is ground. The tooth width in this embodiment is 34 mm. The outer diameter and root diameter of the embodiment are 76.77 mm and 62.50 mm, respectively. The roughing dimension before hard finishing, as a diametrical two-ball dimension with a measuring ball diameter of 6 mm, is 81.150 mm, and the finished dimension corresponding to the final geometry is 80.605 mm, resulting in a stock allowance of 125 µm per flank.

[0042] The grinding tool is a two-component tool, as described in... Fig. 2 shown is a three-start grinding worm with an engagement angle of 20° in this embodiment.

[0043] The cutting speed was set to 50 m / s, the machining strategy is one with three grinding strokes, of which two roughing strokes with worm area 10a and one final pass with worm area 10b were used.

[0044] In this specific embodiment, the radial infeed was initially 0.237 mm in the first roughing pass, then 0.179 mm in the second roughing pass. The machine-set radial infeed in the third machining pass was 0.070 mm. The nominal stress volume Qw in [mm³ / s] was 65.5, 43.7, and 43.4 in the sequence of strokes, with a feed rate of 0.273, 0.241, and finally 0.846 mm per workpiece revolution, also in this sequence. Relatively speaking, the feed rate in the last machining pass is therefore significantly higher than in the preceding roughing passes. This allows for overall shorter machining times and correspondingly much better cycle times than conventional methods, in which a finishing pass is interspersed after roughing.

[0045] Surface quality measurements of the machined gear teeth 4 were performed using a Hommel-Etamic Turbowave V7.60 (probe TKU 300, measuring range 400 µm, probe length L t 4.80 mm, speed (V t ) 0.5 mm / s, recording 24,000 measurements with a PRW-profile filter according to ISO 11562 with L c (cut off) of 0.800 mm with L c / L s :OFF probe:r=5 µm / 90°).

[0046] For the material component R-profile (Abbott curve), the following was used: Fig. 3a The curve shown on the right flank was determined; surface parameters were R a = 0.09 µm, R z = 0.71 µm.

[0047] In a second embodiment, a two-stroke strategy was used, with one stroke each with worm section 10a and 10b. The gear data here were module 1.275 mm with 36 teeth, pressure angle 18°, helix angle -22° with a gear width of 16.6 mm, outside diameter 51.98 mm and root diameter 45.40 mm.

[0048] Here, a preliminary machining dimension (in the diametrical two-ball dimension M dk with a measuring ball diameter of 2.5 mm) of 53.803 mm was removed to a finished dimension of 53.275 mm (corresponding to a stock allowance of 0.099 mm per flank). A five-start grinding worm with a pressure angle of 18° was used as the tool; the cutting speed remained unchanged compared to the first embodiment.

[0049] As further process parameters in strokes 1 and 2, a machine axis setting for the radial feed of 0.306 mm and 0.065 mm was set, respectively, the feed per workpiece revolution was 0.227 and 0.948 mm with a nominal material removal rate of 45 and 40 mm³ / s.

[0050] The machined gear teeth were also measured, with modified measuring parameters regarding sensing distance of 1.50 mm and speed of 0.15 mm / s and L c 0.250 mm.

[0051] In this way, a value of 0.07 µm was determined for Ra and a value of 0.51 µm for Rz; the Abbott curve for the right flank is in Fig. 3b The image shows a core roughness depth Rk of 0.22 µm, a reduced peak height Rpk of 0.08 µm, and a reduced groove depth Rvk of 0.11 µm.

[0052] In both embodiments, the surface qualities desired by the user could thus be achieved and even exceeded, while still maintaining favorable machining times by eliminating the usual finishing pass of the pre-machining tool, preferably with ceramic bond (screw section 10a).

[0053] Furthermore, the invention is not limited to the embodiments explicitly set forth in the preceding description.

[0054] Although the invention has been described in more detail in specific embodiments for continuous gear grinding, the process mechanisms and features described in the introduction are also applicable to other hard finishing processes for gears.

[0055] Furthermore, the tools for roughing and machining with compliant bearings and compressive preload do not need to be a combination tool as in Fig. 2 As shown, it can also be implemented using separate tools that are clamped together in a grinding head, or that are provided in separate grinding heads, just as other grinding machine configurations such as those in Fig. 1 can be used as shown.

Claims

1. A method for cutting a toothing (4) from a metal workpiece (2), in particular in continuous generating grinding, in which a tooth flank, still having an oversize compared with its predefined final geometry, of the toothing (4) is hard finished, in one or more cutting passes in cutting engagement with in one or more cutting tools (10) fed thereto with a geometrically undefined cutting edge made of cutting grains incorporated in a binder matrix, in order to produce, in the final geometry, a reflective property of the surface of the tooth flank, characterised in that in a cutting pass of a cutting tool (10b), both an elastically resilient arrangement of the cutting grains set by its binder matrix acts on the surface property of the tooth flank, and a cutting reduction of the oversize by at least 2 µm at the tooth flank is realised by a compressive preload, due to the infeed of the cutting tool, to which the cutting engagement is subjected, wherein the compressive preload is effected by an appropriate radial overfeed of at least 20 µm and no more than 100 µm as a reference-related, negative oversize compared with the final geometry.

2. The method according to claim 1, in which, in said cutting pass, more than 3 µm, preferably more than 4 µm, in particular more than 5 µm oversize is removed, and / or less than 12 µm, preferably less than 10 µm, in particular less than 8 µm oversize is removed.

3. The method according to claim 1 or 2, in which the elastically resilient behaviour is based on the material chosen for the binder matrix as a plastic material or a rubber material, in particular polyurethane.

4. The method according to one of the preceding claims, in which, for the modulus of elasticity of the cutting tool, a value, measured in GPa, of less than 20.0, preferably less than 18.5, in particular less than 17.0 and / or greater than 10.0, preferably greater than 11.5, in particular greater than 13.0 is used.

5. The method according to one of the preceding claims, in which the compressive preload is effected by means of an appropriate radial overfeed of at least 28 µm, in particular at least 36 µm and / or no more than 90 µm, in particular no more than 80 µm, as a reference-related, negative oversize beyond the final geometry.

6. The method according to one of the preceding claims, in which the cutting grains of said cutting pass have a Knoop hardness in N / mm2 of more than 23,000, preferably more than 25,000, in particular more than 27,000.

7. The method according to one of the preceding claims, in which the cutting speed (vc) measured in m / s of said cutting pass is greater than 42, preferably greater than 45, in particular greater than 48, and / or less than 80, preferably less than 72, in particular less than 66.

8. The method according to one of the preceding claims, in which the grain sizes of the cutting grains are within a range greater than 5.5 µm, in particular within a range greater than 7.5 µm, further preferably within a range greater than 8.5 µm and / or the grain size is less than 18 µm, preferably less than 16 µm, in particular less than 14 µm.

9. The method according to one of the preceding claims, in which an average roughness depth (Rz) indicated in µm of the surface after said cutting pass is less than 1.2, preferably less than 1.1, further preferably less than 1.0 and in particular less than 0.9.

10. The method according to one of the preceding claims, in which said cutting pass is a subsequent cutting pass immediately preceded by a cutting operation which reduces the oversize by a total of more than 30 µm, preferably more than 50 µm, in particular more than 70 µm in one or more cutting passes.

11. The method according to claim 10, in which said preceding cutting operation comprises a maximum of two cutting passes, in particular only one cutting pass.

12. A use of a gear-cutting tool (10), designed for a method according to one of the preceding claims, for finishing / hard machining of a toothing (4) in a method according to one of the preceding claims.

13. The use according to claim 12, in which the gear-cutting tool has a first cutting region (10b) for the preceding cutting operation according to claim 10, and a second cutting region (10a) for the subsequent cutting pass according to claim 10.

14. The use according to claim 12 or 13, in which the gear-cutting tool has the form of a worm (10) designed in particular for generating grinding.

15. A machine tool (100) for cutting a toothing made from a metal workpiece, comprising a control device (99) which controls the machine tool for carrying out a method according to one of claims 1 to 11, in particular using a gear-cutting tool in accordance with the use according to any of claims 12 to 14.

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